Several polymer processing techniques use solid-state stretching in creating final products. Non-limiting examples include thermoforming, drawn tape, drawn monofilament, machine direction oriented (MDO) film, biaxially oriented film (such as through double bubble processing and tenter frame stretching), solid-state extrusion and injection stretch blow molding. Traditionally, these processes deform a starting article at a temperature below its melting temperature, shaping it into a final desired shape.
Injection stretch blow molding (ISBM) is a subset of solid-state stretching. ISBM may eliminate flash trimming and the regrind that is reused in conventional extrusion blow molding (EBM). ISBM often produces more precise bottle threads because those are formed through the injection molding step. The solid-state stretching step may produce a stiff bottle with exceptional top-load properties and other improved physical properties, which may allow downgauging/lightweighting. In addition, surface smoothness may be improved by articles made by ISBM, thereby improving printability and print quality. Further, a smooth surface provides proper label adhesion in molded articles such as bottles. Because ISBM bottles are stretched in the solid-state, the need for melt strength may be reduced or eliminated. A resin not well suited for conventional EBM may be well suited for ISBM.
ISBM commercial lines can produce thousands of bottles in an hour. To realize such rates, resins typically used for ISBM have excellent processability. Other resin characteristics may include ready stretchability and few failures during the stretching and blowing step.